Three-dimensional microtomographic study of Widmanstätten microstructures in an alpha/beta titanium alloy

Branch Elimination during Heat Treatment of Titanium Alloys with a Colony-Alpha Microstructure

“…By contrast, classical coarsening of an aggregate of lamellae is a much more difficult problem because of the irregular plan-view shapes of typical alpha platelets, the complex spatial arrangement of the platelets within a colony relative to each other, and the irregular shape of the colonies themselves. [8] As a first effort in developing a quantitative description of platelet thickening, the kinetics of the elimination of branches during the heat treatment of the alpha/beta titanium alloy Ti-6Al-4V were determined and interpreted in terms of an approximate diffusion analysis. The program material comprised 12.5-mm-diameter hot-rolled bar with a measured composition (in weight percent) of 6.33 aluminum, 4.07 vanadium, 0.19 iron, 0.16 oxygen, 0.01 carbon, 0.01 nitrogen, 0.005 hydrogen, and balance titanium.…”

Tri-modal microstructure evolution of TA15 Ti-alloy under conventional forging combined with given subsequent heat treatment

“…One reason is that WQ will result in a large amount of s nuclei and scattered distribution, and growth of ˛s in the longitudinal direction is restricted. The other reason is that there are some holes and concave structures on the broad face of lamellar s as reported by Sharma et al (2010) and Vanderesse and Maire (2008), so during long time holding at 930 • C the holes will expand and lead to fracture for further spheroidization. In addition, ˛ phase nucleated on part of the ␤ boundaries and spheroidized into individual equiaxed ˛p gradually, leading to an increase in the volume fraction of ˛p further.…”

Multistage Segmentation of Lamellae Colonies Based on Directional Filter Bank and PCA Analysis

“…The algorithm has been already used by Jeulin and Moreaud [7] to extract local gradient map which in turn is an input for PCA to detect orientation discontinuities in textured images. This has been further coupled with a semi-automatic watershed-based method to separate α-colonies in microtomographic images of titanium alloy [14]. The algorithm for extraction of local orientation map I or can be presented in the following several steps: calculate the co-variance matrix, using pixels from neighborhood defined in a window of size w × w centered on p, 4: calculate the eigenvectors and eigenvalues from the co-variance matrix, 5: calculate local orientation I or (p) of pixel p defined as the angle between the eigenvector corresponding to the largest eigenvalue and a reference vector (versor of y-axis).…”